Cummins is headquartered in the US. Over 55% of their market is outside the US. They source castings and parts from all corners of the world. They are truly a global company.
It is common for people to place China and Japan in the same category of quality, but the opposite is actually the case. Honda (Japan) makes the most engines per year, of any company in the world. I have worked for a Japanese company for over a decade now, and their discipline to engineering design and manufacturing for end result quality is nothing less than amazing. If a finished pallet of our product is dropped, even though it is packaged properly and each item is padded, the entire pallet of product is put into the shredder. This can be at a price of up to $70,000 per pallet.
I don't know for sure, but I would guess the engine starved of oil, went over RPM, or something impacted the rod first. It could have also possibly been dropped and caused an inclusion, which then later broke. On a rebuild, somebody could have stepped away to grab a phone call, and forgot to tighten the rod cap bolts to spec, and simply went on to the next rod.
Japan had steel refined before almost any other country in the world, and this is with virtually no natural resources on their island country. Samurai sword is a prime example.
